A week today the nation goes to the polls. Here Political Editor Richard Porritt takes the temperature of the battle to form the next government as campaigning reaches a climax.

Why believe the polls?

Polling firms confidently predicted the 2015 election, the European Union referendum and the US presidency – and almost every one got those contests completely wrong.

Mid-campaign in 2015 the Guardian ran three polls across its front page each showing Labour leading the Tories. The bullish headline read: 'The day the polls turned.'

And the paper was right – the polls had turned. But the voters had not. When the far more reliable exit poll was announced after voting had closed people were so convinced it was going to be close many refused to believe what was then seen as a shock prediction. The exit poll was right, of course – the polling throughout was flawed.

Norwich Evening News:

Most poll leads contract during a campaign. Lots of political scientists have theories as to why but the truth is no-one can be certain. Another oddity is how so many polls taken just before the announcement of an election mirror the most important one at the end. Polls during campaigns have a somewhat chequered history.

But the YouGov/Times data predicting a hung parliament, which has electrified an already fascinating campaign, is different. It stands out because the method is new. We will not know until June 9 whether this marks a polling revolution or an all time low.

The model used is called Multilevel Regression and Post-stratification – or MRP. Instead of polling several thousand people from different backgrounds and projecting that across the whole country, MRP collects data from a small number of people in every constituency. To those results further, traditional data is added. This method was tested during the referendum and consistently predicted the Leave vote.

But at the same time more traditional methods, including other polls done by YouGov, offer some uniformity – they all show a strengthening Labour vote.

In the marginals in Norfolk YouGov's model predicts Lib Dem Norman Lamb will hold North Norfolk and Labour's Clive Lewis will increase his majority in Norwich South.

There is no doubt that with polling day looming the nerves are jangling at Conservative Campaign Headquarters. And rightly so.

The Tories have let Labour back into an election race they should have had sewn up weeks ago. Jeremy Corbyn has grown into this campaign mainly due to the fact that Mrs May has faded.

The cracks were starting to show even before the manifesto launch. Every passing interview with the staccato repetition of 'strong and stable' made the PM seem anything but. And yet even when her robotic mantra was mentioned by interviewers she carried on repeating the line – she is still doing it now. Add to this her natural awkwardness in high-pressure situations and Mrs May looks like a terrified youngster on their first day at school trying to bluff confidence in front of her new teachers and classmates.

Under the intense scrutiny of an election campaign Mrs May has not excelled, in fact she has floundered.

The Tories are desperate for this campaign to get back to Brexit like they planned. They believe that is where Mrs May's supposedly strong leadership will win the party votes. And when faced with the question 'who would you prefer to have around the EU negotiating table?' most of the polls have Mrs May as a clear winner over Mr Corbyn.

But you can't plan general election campaigns – things happen that throw them off course. And it is this unpredictability that seems to terrify Mrs May. The Labour leader, on the other hand, is having a solid campaign. Not only did Mrs May overestimate her own electability she also underestimated Mr Corbyn.

But will it be enough to cause a huge shock and send Labour back to Downing Street? Perhaps not. But even in victory, which very much remains the most likely outcome for Mrs May, she will reflect on a campaign where she choked. The Tories are fully aware that against a stronger Labour Party with a more centrist manifesto they would have been spooked by more than just the odd poll.

This election looks set to throw up more losers than winners whatever happens.